| Position 1 | Position 2 | Position 3 |
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The basic position in which a stone can be captured in geta (or net) is shown in Position 1 of Fig 1-1. Notice the marked white stone - it cuts the black shape into two separate groups. This makes the stone important! Black would be very happy indeed if he could find a way to capture this offending white stone. And there is a way - the technique is called geta in Japanese (or net in English). Black can kill the marked stone by simply playing at 'a' - and there is no escape for white, as illustrated in Position 2. Position 3 shows the resulting situation after white stones are killed (the x's denote the killed white stones).
| Position 1 | Position 2 | Position 3 |
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Geta can come in many forms and shapes. Two more of them are shown in Fig 1-2 - in both position white can capture the marked black stones in a geta by playing at '1'.
| Position 1 | Position 2 |
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The next technique for killing stones which I want to talk about is the shicho, or ladder. Where geta provides a method of capturing stones with only one move, to capture a stone in shicho requires two moves - and so geta is superior to shicho. Unfortunately, there are positions in which geta does not work, and the possibility of shicho has to be examined. Let us look at Position 1 of Fig 2-1. It is a relatively simple exercise to find out that black cannot capture the marked white stone in geta with 'a'. So he has to initiate the shicho sequence with 'b'. The continuation is shown in Position 2, and the result in Position 3.
| Position 1 | Position 2 | Position 3 |
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As you can see from Fig 2-1, the idea of shicho is to always block the opponent's group liberties in a zigzag fashion, so his group is constantly in atari. This produces a pattern of stones running towards the edge of the board in a ladder-like fashion (thus the name - ladder). However - this pattern or "running towards the edge" presents one weakness: instead of running with the ladder and have his stones hopelessly lost, white can abandon the ladder and play a ladder block! A ladder block is a stone which is placed in the path of the potential ladder, and which disturbs the pattern so that the ladder does not work. An example of such ladder block and what happens if black ignores it and pursues the ladder is shown in Fig 2-2.
| Position 4 | Position 5 | Position 6 |
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In Position 4, white plays a ladder block with '2'. This renders the ladder unworkable - and what happens if black fails to take this into account and cluelessly plays an unrelated move like '3' is shown in Position 5 - not only has the white stone escaped the ladder, but now it seems that it is black's marked stones which are in grave danger. The sequence is a great success for white - all because of black's failure to account for the ladder block at '2'.
So - what should black have done instead of Position 5? Why - Position 6, of course! After the ladder is broken with white '2', the only thing that black can do is to capture the white stone immediately with '3' in Position 6. White will probably strengthen his solitary stone (which performed its duty as a ladder breaker splendidly) with a move like '4' and the game will continue.
Conclusion:
Be aware of ladder breakers!!
Any stones, yours or enemy, placed along the
path of the ladder will have an influence on it! There is always a
possibility of a ladder block, placed either for this special purpose,
or appearing in due course of some other battle in another area of the
board. For this reason, to capture a stone in a ladder, you will
have to make two moves - one to initiate the ladder (like black '1' in Position
3 or in Position 4) and one to finish it off by actually
capturing the stone (like black '3' in Position 6).
As said above, to capture a stone in a geta, you only need one move - and this constitutes the major advantage of geta over a shicho. Therefore, when faced with a necessity to capture a stone, look for a geta first - and if no geta can be applied, then look for a ladder!
Snap-back, as the name indicates, is a situation in which a group of stones cannot be rescued from atari by killing an opponent stone, even though this stone is itself in atari! Confusing? Well... lets look at some examples.
| Position 1 | Position 2 | Position 3 |
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In Position 1 of Fig 3-1 the two marked black stones are in atari. Can black save them? It seems that if black plays at 'a', killing the single white stone, black could save his two warriors. Well - this move is shown in Position 2 - the 'x' denotes the killed white stone. How many liberties do the black stones have now? Right - still only one liberty, and it is white's move!! Bummer... If white plays as in Position 3, the three black stones are captured, proving that there is no escape for the two black stones in Position 1. True, one could argue that black has now also captured a white stone, but this is balanced by the fact that white captured three stones instead of the initial two - so the result is the same.
Conclusion:
Stones caught in a
snap-back are terminally dead - there is little use in trying to rescue them! It is better to just abandon them and play elsewhere - who
knows, maybe a move like black '1' in Position 2 will come in
handy as a ko threat in the future?
Some more examples of snap-backs are given in Positions 4-6 of Fig 3-2. The situation in Position 6 is familiar from our discussion about the cuts on the second line (in Chapter #3 of Go Techniques, Position 3 in Fig 3-1). In each case black's move at '1' initiates a snap-back and white's move at 'a' does not save the marked white stones.
| Position 4 | Position 5 | Position 6 |
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